The present invention relates to a process for producing ethylene dichloride. More specifically, it relates to an oxychlorination process in which ethylene is reacted with hydrogen chloride and oxygen in the presence of a catalyst.
1,2-dichloroethane (ethylene dichloride) is used extensively for producing vinyl chloride.
Accordingly, intensive research has been made by those skilled in the art relating to the production of 1,2-dichloroethane. A process which is widely used in industry is the oxychlorination process in which ethylene is reacted with oxygen and hydrogen chloride in the presence of a catalyst such as copper dichloride. Extensive patent literature exists relating to the catalysts in the process and to the process technologies which, among others, try to maximise yield of ethylene dichloride. The by-products from existing processes are usually burnt and hydrogen chloride is recovered. Although the yield of ethylene dichloride is quite high, generally between 90 and 97 percent, depending on the process type and conditions, the incineration of the by-products in large scale production is a problem for the environment.
European Patent No. 0 005 655 suggests oxidative destruction of the by-products using a catalyst containing platinum or iridium on a support of alumina having the eta crystallographic structure to improve the incineration process.
However, incineration of the by-products remains uneconomical and efforts are necessary in order to keep the pollution of the environment to a low level.
In European patent application 0 132 971 an oxychlorination process is disclosed wherein hydrogen chloride gas and oxygen are reacted with an unsaturated organic compound. Chlorine containing organic residues are combusted in an oxygen-rich flame whereby hydrogen chloride is produced which is recycled to the oxychlorination process. However, this process is rather inconvenient because a high combustion temperature of more than 2000.degree. C. is required to ensure complete destruction of the residues. European patent application 0 132 971 discloses that steps must be taken to avoid corrosion of the chamber material in the presence of hydrogen chloride.
In the German Auslegeschrift DE-AS-24 00 417 it is suggested to adsorb the by-products of the oxychlorination process partially on activated carbon and to burn the nonadsorbed by-products such as ethylene at a temperature between 500.degree. C. to 2000.degree. C. The adsorbed impurities such as ethylene dichloride and ethyl chloride are then desorbed with vapour.
However, a careful separation of vapour and chlorinated by-products is required after the desorption step in order to avoid pollution of water.
Accordingly, it would be desirable to overcome these disadvantages of known oxychlorination processes for producing ethylene dichloride.
It has been found that the problem of by-products disposal can be reduced by separating ethylene dichloride and ethyl chloride (which is one of the main by-products in the oxychlorination process) and then converting ethyl chloride to ethylene and hydrogen chloride in the presence of a catalyst.